The invention relates to the sampling of gas above a scrubber. These samples are used to determine the particulate concentration in the gas leaving the scrubbers. When permanent straightening vanes are used in scrubber stacks, laminar gas flow occurs resulting in droplets being carried out of the stack. These droplets might otherwise impact the walls and flow out with the scrubber effluent. The methods for sampling particulate cannot distinguish between dust and other particles in a gas stream and dust in the slurry droplets. This may result in sampling results being biased high. The removal of the flow straightening device allows the swirling of the gases to impact the droplets upon the stack wall. The slurry is thus contained within the scrubber.
The present invention provides a method for the installation of temporary vanes which when installed provide axial gas flow ideal for the sampling of particulate. Because the vanes are removed during normal operation, the amount of droplets leaving the top of the stack is significantly reduced. This eliminates dirty rain from the stack, a pollution hazard itself. More importantly, the few droplets which are carried out of the stack are substantially without any solids in them as compared with the significant amount of dust in such particles where the straightening vanes are permanently installed.